Practicing any of these techniques may improve welding quality and durability. 

The first major failure of MIG welds is porosity. The most common causes of pores are dirty, oily, and painted surfaces. All these contaminants are trapped in the weld, resulting in the formation of sponge-like holes. "Farmers often fail to adequately prepare the metal before welding," said John Lesner of Miller Electric. "This includes sanding or removing paint, rust, dirt and other surface contaminants, as well as the complete sanding of cracks, usually beyond the immediate visible range." 

Collier considers this to be the most common failure of MIG welding. "Your welder doesn't care if your grounding is bad. Whether your welding gun is spattered or intermittent, it will continue to pull out the wire," he explained. 

Karl Hoes of Lincoln Electric says that a welding arc requires current to flow smoothly through the circuit. The welding current will find the path of least resistance. Therefore, if the welding ground is accidentally placed close to the arc, the current may find another path. Connect the clamp firmly to the bare metal as close as possible to the arc.

Generally, keep the distance that the wire extends from the end of the contact tip of the spray gun between 1/4 to 3∕8 inches. "This simple tip can have the greatest impact on your MIG welding," said Jody Collier. 

"Use your hands as much as possible," Collier urged. "Support the curved part of the gun neck with one hand and the trigger part with the other hand. When your prop hand is close to the weld, please don't hesitate. If necessary, please buy heat-resistant heavy-duty welding gloves." 

When soldering, the music in your ears should be a steady hum. Leisner pointed out that a steady hiss may indicate that your voltage setting is too high. "A loud, harsh sound may indicate that the voltage is too low. The crackling sound of the machine gun indicates that the amperage setting is too high," he added.

"For better penetration, keep the arc at the leading edge of the molten pool," Collier said. 
    

The exception to this rule is when welding thin metal plates. In this case, keep the arc farther in the molten pool to prevent burn-through.

Surprisingly, this basic match is often overlooked. If you try to pass a 0.030 diameter welding wire through a 0.035 roller, you will find yourself constantly changing the feed rate and will never be able to set it correctly because the grooves on the roller are too large. The same advice applies to spray gun cable gaskets and contact tip sizes.  

The most common method is to push the gun in the direction of the weld (forehand method). Forehand welding produces a shallow penetration with a flat, wide, smooth surface. 
   

The second method is when you drag the gun (backhand method). This produces a deep penetration weld with a narrow and high center. 
   

So what method should you use? It depends on the thickness of the metal you want to weld and the depth you need to penetrate the weld. 

If you are doing vertical, horizontal or overhead welding, “keep the weld pool small for best bead control and use the smallest wire diameter possible,” Leisner said.

"Contact tips are cheap," Collier said. "Put a bag in your toolbox and change it often." Worn contact tips are usually oval, which can cause irregular arcs. In addition, if the tip enters the molten pool, it should be replaced immediately. For most temporary welders, a good rule of thumb to ensure high-quality welding is to replace the welding tip after 100 pounds of welding wire has been consumed. 

Leisner says that you can learn a lot by looking at the completed weld bead. 
   

Convex shapes or sticky beads usually indicate that your setup is too cold for the thickness of the repair and is not generating enough heat to penetrate the base material. Concave beads indicate a problem with heat input. 

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